1. Field of the Invention
The present invention relates to an image forming apparatus having a preview function for previewing an image before it is printed out.
2. Related Background Art
High image quality and sophisticated functions of digital color copiers are becoming more common. A color adjustment process and an editing process for an output image at present meet most of requirements of users. Copiers having a so-called preview function are also being manufactured. With this preview function, instead of printing out an image several times in order to confirm the edited image or adjusted color, an image is displayed on a CRT or the like for confirmation of such editing and adjustment.
There are copiers having a monochrome liquid crystal display. For a color copier, however, a preview system of full-color is desired in order to adjust colors.
One example of a preview system is shown in FIG. 45. Blocks 1101 to 1109 constitute a full-color copier, and blocks 1110 to 1111, and 1219 constitute a preview system.
In FIG. 45, reference numeral 1101 represents an RGB output sensor for reading a reflection original, reference numeral 1102 represents an S/H and A/D converter, reference numeral 1103 represents a shading correction circuit, reference numeral 1104 represents an input masking circuit, reference numeral 1105 represents a LOG converter circuit, reference numeral 1106 represents a masking UCR for adjusting the colors to match the printer characteristics, reference numeral 1107 represents an image editing circuit for performing various processes such as trimming, masking, painting, and a variable power process, reference numeral 1108 represents an edge emphasis circuit, and reference numeral 1109 represents a printer unit for scanning a reflection original three or four times to print out a full-color image.
Reference numeral 1110 represents an image memory unit for storing image signals (RGB) after input masking 1104, reference numeral 1111 represents a memory control circuit for controlling the image memory 1110 (the memory control circuit having an address counter and controlling data transfer between an unrepresented CPU and image memory), and reference numeral 1219 represents a CRT for displaying data stored in the image memory. If a read image is simply displayed on a CRT, a desired editing process entered from an operation unit is not reflected in the image. Therefore, the system is configured so that data in the image memory 1110 can be accessed by an unrepresented CPU to perform the process equivalent to the circuit 1107 and display the final processed image.
High speed requirements for a digital full-color copier are steadfast. In order to meet the requirements, a color LBP has been proposed in which four photosensitive drums are used as shown in FIG. 1 and development units for Y, M, C, and K colors are used. Such a color LBP is necessarily required to have an image memory for correcting a spatial displacement among the drums. It is desired to have a full-page image memory in order to perform more sophisticated image processing.
As the image processing function attains a high quality, it is difficult to predict how an image is actually printed out. There may sometimes be a difference between the printed image and the predicted image, and unnecessary copies increase.
In a two-page separation mode of sequentially copying right and left pages of an opened original document, in a multi-page enlargement mode of dividing one original into a plurality of block regions and enlarging and copying an image of each block region on multiple sheets, or in a mode of sequentially forming an image on multiple sheets, it is difficult to know in what order each image is copied, and copied sheets are required in some cases to rearrange their order.